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Jan. 16, 2012 -- Machines that help keep the airways open during sleep may be lifesaving devices for women with severe sleep apnea, a new study suggests.

People who have obstructive sleep apnea (OSA) stop breathing many times during the night. It is much more common in men than in women.

The struggle to start breathing again causes sufferers to snore loudly, snort, or gasp. That often keeps their bed partners from getting rest.

But there’s a greater danger to sleep apnea. It’s a major stress for the heart.

Studies in men have shown that OSA greatly increases the risk of events like heart attacks and strokes.

Researchers weren’t sure if sleep apnea also increased those risks in women or how much treatment of the condition would help.

The new study, which followed more than 1,100 women in Spain for an average of five years, found that women with untreated, severe sleep apnea had 3.5 times the risk of dying from a heart problem or stroke compared to women without the condition.

But treating those breathing interruptions with a continuous positive airway pressure (CPAP) machine, which uses pressurized air delivered through a mask to hold the throat open, appeared to even their odds.

Women who used CPAP machines for at least four hours a night had the same risk of dying from a heart attack, stroke, abnormal heart rhythm, or from heart failure as those who did not have the condition.

“I thought this was a good, quality study. It was well designed,” says Milena Pavlova, MD, a neurologist at Brigham and Women’s Hospital in Boston.

“It’s a good thing that they focused on women because a lot of previous research, by taking all comers, ends up having a much higher number of men,” says Pavlova, who studies sleep disorders in women, but was not involved in the research.

“Now we know that sleep apnea is associated with worse [heart disease and stroke] outcomes for women,” and that treatment is associated with reductions in those risks, she says.

Studying the Benefits of CPAP Treatment in Women

For the study, researchers followed women who were referred to sleep clinics in Spain over a nine-year period.

The women were in their 50s and 60s when the study started. And most were overweight or obese. Obesity is known to increase the risk for breathing problems during sleep.

And about 1 in 5 reported that they’d already had a cardiovascular event, like a heart attack or stroke.

During sleep studies, researchers monitored the women and counted the number of times their breathing slowed or stopped for at least 10 seconds at a time.

Women with 10 to 29 breathing interruptions per hour were classified as having mild to moderate sleep apnea. Those with 30 or more interruptions per hour were told they had severe sleep apnea. Women who scored less than 10 were considered not to have sleep apnea and were used for comparison.

Every patient with severe sleep apnea was offered treatment with a CPAP machine that uses a pressurized flow of air to hold breathing passages open during the night. Women with mild to moderate sleep apnea were offered CPAP if they reported being sleepy during the day.

Counters on the machines told the researchers how long the women were using them at night.

During the study, 41 patients died of heart-related causes, including heart attacks and strokes and from heart failure.

Researchers discovered that women with severe, untreated sleep apnea -- meaning they didn’t use their CPAP machines, or used them for less than four hours a night -- had more than three times the risk of dying from a heart problem as women who didn’t have sleep apnea.

That was true even after researchers accounted for other things that influence the risk of heart disease, including age, body weight, high blood pressure, diabetes, and previous heart attacks or strokes.

Women with severe sleep apnea who used a CPAP machine for at least four hours a night saw no increase in their risk of heart or stroke-related death, however. They had the same risk as women who didn’t have sleep apnea.

“For patients with obstructive sleep apnea, adequate CPAP use is as important for their [heart] health as the pills they take for hypertension or diabetes,” researcher Francisco Campos-Rodriguez, MD, from the department of respiratory medicine at Valme University Hospital in Seville, Spain, says in an email to WebMD.

The retail cost of a CPAP machine runs from $400 to $800, but insurance plans may pick up the tab if it’s prescribed by a doctor.

Why Is Sleep Apnea Bad for the Heart?

Experts aren’t entirely sure why sleep apnea is so bad for the heart, but they have some working theories.

“There are two pathways through which it can worsen health. The first is through low oxygen, the second is through the frequent arousals,” says Pavlova.

But studies in animals have shown that interrupted breathing can lead to periods of low blood oxygen.

This low oxygen is thought to trigger the body’s fight-or-flight response, which raises blood pressure in the lungs and makes blood clot more easily, increasing the risk for events like heart attacks and strokes.

A second problem is that the body has to fight to breathe once the airway gets blocked.

“As a result of the strain to breathe, there is a response from the body to wake up, to take a better breath,” Pavlova says.

Recognizing Apnea Can Be Harder in Women

Even though sleep apnea can have serious health consequences, it often goes undiagnosed.

Partly, that’s because people with apnea aren’t aware that they snore or gasp as they start or stop breathing. Often a bed partner is the one to notice those symptoms.

And doctors may not spot the condition during a routine exam because women’s symptoms may seem different than men’s.

Pavlova says women with apnea are less likely to complain about daytime sleepiness than men are, for example.